In dentistry, there has been a shift in recent years from a philosophy of drilling and filling to one of prevention and cosmetics. By way of example, many people today are choosing to have clinical procedures done to enhance their smile and appearance. Most of these procedures involve the modification of tooth shape, alignment, and/or color.
The use of intraoral video and/or imaging systems (hereinafter xe2x80x9cintraoral camera systemxe2x80x9d) has grown rapidly in dentistry over the past few years. Such systems are widely utilized in xe2x80x9cshow and tellxe2x80x9d settings, i.e., where the dentist can show and illustrate particular features of a patient""s mouth. These intraoral camera systems are rapidly becoming key complex diagnostic and treatment planning. Presently, approximately 30% of the practicing dentists in the age group between about 35-54 own and utilize intraoral camera systems. It is expected that that percentage will only increase with increased familiarity. See Dental Procedures Report, pgs. 22-24, February 1995.
A necessary step in altering a patient""s tooth color is to determine the xe2x80x9cshadexe2x80x9d of the existing tooth. For example, those persons seeking a whiter, brighter smile are still assessed to establish their existing tooth color so that an appropriate before and after comparison can be made. Shade determination is even more important for those persons seeking reconstructive work, since one goal of the reconstructive process is to achieve a natural appearance. Therefore, it is important to know the existing tooth shade so that it can be accurately matched with the new restoration.
The dental profession utilizes standardized shade guides created by those companies which manufacture the reconstructive materials. One well-known shade guide is the Vita(trademark) shade guide, which includes sixteen different shades. Other, less popular shade guides include those guides provided by Bioform(trademark) and SR-Vivadent(trademark).
These shade guides are utilized in a rudimentary fashion. The guide itself is a plastic plate with a plurality of removable color tabs that are shaped like a tooth, e.g., the front tooth. Typically, to assess a patient""s tooth shade, a dentist removes one of the colored tabs and holds it up to the patient""s tooth so that she can xe2x80x9ceyeballxe2x80x9d the closest match possible. Understandably, there are many variables to this method, some of which stem from the subjectivity of the dentist making the eyeball assessment.
Once the tooth shade is determined, the information is used relative to the particular procedure needed. In bonding or filling a tooth, for example, the composite materials required for the restoration are specified within the range of the shade guide, e.g., one of sixteen shades for the Vita(trademark) range. More particularly, if a crown, bridge or denture is needed, the patient""s shade must be determined and communicated correctly to the lab that make the crown, bridge or denture.
The communication of shade information between the dentist and the lab is extremely important. Often, there is a break-down or failure in this communication, resulting in a poor shade match for the patient. In some cases, a particular dentist utilizes an uncommon shade guide, thereby leaving the lab technician to eyeball and convert the shade information to a Vita standard shade (since porcelain is often made from the Vita(trademark) shade guide). This too can result in improper shade matching.
The process for selecting the porcelain for a particular tooth shade illustrates the difficulty in assessing and manufacturing the correct color match. If, for example, a crown of Vita(trademark) shade A3 is desired, porcelain is built by hand with a paint brush onto a model of the tooth to be restored. The porcelain is built in layers on the model to achieve translucency and natural appearance. Each layer has a particular color and intensity associated with it. To generate shade A3, the technician follows a xe2x80x9crecipexe2x80x9d that is given by the manufacturer Vident(trademark), requiring a different shade for each layer of porcelain applied. If a doctor asks for a shade that is not a Vita(trademark) standard shade, the technician typically seeks to achieve that shade by combining different porcelain shade combinations together, to increase or decrease the chroma, hue and value of the shade.
To further complicate the color-matching process, some dentists are simply not skilled in taking and determining shade information. Therefore, these dentists sometimes send their patients directly to the lab where the technician can determine the shade information. Alternatively, these dentists sometimes have a technician come to their office. In either event, there is, at times, one more level of subjective uncertainty injected into the correct match and determination of a patient""s tooth shade. Thus, there is a need for more improvements in this area.
The invention relates to a method for determining a patient""s tooth shade comprising the steps of electronically imaging a patient""s tooth to obtain an image which includes color information representative of tooth color; determining the patient""s tooth color from the color information of the image; and displaying the determined tooth color to identify one or more tooth shades having a combined color corresponding to the determined tooth color.
Preferably, the displayed data includes RGB chromaticities of the color image, and the patient""s tooth color is determined by averaging the color information at selected locations of the image which correspond to different spatial locations of the patient""s tooth. If desired, the color information of the patient""s tooth can be electronically stored for use at a later time.
The identification of tooth shade(s) is generally made by comparing the determined tooth color to a plurality of electronically stored tooth shades. If desired, both the identified tooth shade(s) and the color information of the image of the patient""s tooth can be electronically displayed to enable a visual comparison to be made therebetween. Preferably, information which includes the identified tooth shade(s) can be communicated to a laboratory for use in manufacturing a reconstructed tooth for the patient. This is typically done by painting one or more porcelain layers onto a model of the patient""s tooth, each of the layers of porcelain corresponding to the identified tooth shade(s) or a color fraction thereof.
For optimum results, either the patient""s tooth or a tooth shade is imaged at a controlled, reproducible distance, and a reference color to assist in determining the patient""s tooth color from the color information of the image. Also, the patient""s teeth are cosmetically whitened before conducting the electronic imaging step.
Another aspect of the present invention relates to a method for determining a patient""s tooth shade comprising the steps of electronically imaging a patient""s tooth to obtain an image which includes color information representative of tooth color; determining the patient""s tooth color from the color information of the image; and identifying one or more tooth shades having a combined color corresponding to the determined tooth color. The patient""s tooth color can be determined by electronically displaying the color information of the image and by averaging the color information at selected locations of the image which correspond to different spatial locations of the patient""s tooth.
The method may include the further step printing the electronically displayed color information of the image to produce a record or electronically storing the color information of the patient""s tooth for use at a later time. Advantageously, the identification of tooth shade(s) is made by comparing the determined tooth color to a plurality of electronically stored tooth shades, and both the identified tooth shade(s) and the color information of the image of the patient""s tooth can be electronically displayed to enable a visual comparison to be made therebetween. Information regarding the identified tooth shade(s) can be communicated to a laboratory for use in manufacturing a reconstructed tooth for the patient. The reconstruction is performed by painting one or more porcelain layers onto a model of the patient""s tooth, each of the layers of porcelain corresponding to the identified tooth shade(s) or a color fraction thereof.
In order to optimize the color determining step, one of the patient""s tooth or a tooth shade or both can be imaged at a controlled, reproducible distance. The step of isolating the patient""s tooth from stray light can be used to enhance the image. Also, a reference color can be provided to assist in determining the patient""s tooth color from the color information of the image. When used, it is helpful to surround the patient""s tooth with the reference color before the imaging step. Often, the patient""s tooth is cosmetically whitened before conducting the electronic imaging step.
The invention also relates to a system for determining the tooth shade of a patient""s tooth, comprising a camera for capturing an image of the patient""s tooth, the image including color information representative of tooth color; and a shade analyzer sub-system which electrically communicates with the camera. The shade analyzer typically includes a color processor for determining the color of the patient""s tooth from the color information of the image; and a color correlation section for evaluating the color of the patient""s tooth and for identifying a tooth shade having a color corresponding to the color of the patient""s tooth. Preferably, the system further comprises an electronic storage medium for storing shade information representative of a plurality of tooth shades, each tooth shade corresponding to a different tooth color.
The camera is preferably a color CCD camera comprising an array including a plurality of proximately located pixels. Generally, the camera comprises three CCD arrays, each of the arrays collecting image data corresponding to red, green or blue, and the sub-system further comprises a section for integrating at least a portion of the tooth to determine an average color over that portion of the tooth by combining color fractions of known tooth shades. Thus, the color correlation section should include sufficient memory for associating the color of the patient""s tooth with one or more known tooth shades.
Advantageously, the system further comprises a monitor for simultaneously displaying color information of the tooth and tooth shade information so that visual comparisons can be made. Also, a printer can be used for printing the color information displayed on the monitor for communicating this information to a laboratory for reconstruction of the patient""s tooth.
The color processor preferably includes electronic circuitry which determines RGB chromaticities of the color image, each of the plurality of tooth shades has a corresponding RBG representation of the tooth color, and the electronic circuitry quantitatively compares the RGB chromaticities with the RGB representation of each of the tooth shades, thus comparing or identifying a tooth shade based upon a comparison of the chromaticities and the RGB representations. For optimum results, the system further comprises a sample box (or isolation sleeve) for isolating the tooth from stray light. This isolation sleeve preferably includes a first compartment that contains a reference color and a second compartment for receiving the patient""s tooth or a reference shade. It also may have a side wall of a length which assists in obtaining reproducible results by positioning the camera at a controlled distance from the patient""s tooth or the tooth shade. Even without the isolation sleeve, the system may include a reference card having a background color to enhance the image of the patient""s tooth, the card optionally including an opening for receiving the patient""s tooth or a reference shade.